Self-Interference Fluorescence Microscopy (SIFM) is a technique that facilitates depth sensitive and lateral position sensitive fluorescence detection in epi-illuminated confocal microscopy without the need for depth scanning [see, e.g., M. De Groot et al. “Self-interference fluorescence microscopy: three dimensional fluorescence imaging without depth scanning,” Optics Express, 20, 15253 (2012) and C. L. Evans et al., U.S. Pat. No. 8,040,608]. This technique can use a phase plate that converts the wavefront curvature in the back-focal plane of the imaging system into a spectral modulation by via a self-interference. For example, an amplitude modulation on an electromagnetic spectrum that is periodic in the wavenumber domain can be considered as a spectral modulation.
SIFM makes it possible to detect the depth location or lateral position of an emitter with localization error much smaller than the Rayleigh length or the beam diameter, respectively, of the imaging beam or even the wavelength of the detected light.
In the context of biomedical imaging, an efficient implementation of SIFM can facilitate imaging of, for example, near-infrared labeled monoclonal antibodies for tumor detection. The depth sensitivity can strengthen the diagnostic potential with respect to standard confocal microscopy for example by allowing more effective staging of tumors.
In the context of, e.g., single molecule biophysics, an efficient SIFM implementation can facilitate the three-dimensional tracking of particles with nanometer sensitivity.
Previously, the spectral modulation that includes the SIFM signal has been detected with traditional spectrometers that (i) disperse the spectrum in space according to wavelength and (ii) detect the various wavelength components with a large number of detector elements. Although this configuration can facilitate the characterization of the phase and amplitude of the spectral modulation, the use of a spectrometer with numerous detector elements may not be optimal in terms of speed, efficiency and sensitivity.
Traditionally most methods can make use of either spatially or temporally encoded detection of the spectrum with a spectrometer [see, for example A. F. Fercher et al. “Measurement of intraocular distances by backscattering spectral interferometry,” Optical Communications 117, 43 (1995)] or swept-source respectively [see, for example, S. H. Yun et al. “High-speed optical frequency-domain imaging,” Optics Express 11, 2953 (2003)]. Other methods that have been proposed, based on a conversion of a broad-band pulse to a time-domain chirp, can also detect the full spectrum at high sampling density [see, for example Y. Tong et al. “Fibre dispersion or pulse spectrum measurement using a sampling oscilloscope,” Electronics Letters, 33, 983 (1997), P. V. Kelkar et al. “Time-domain optical sensing,” Electronics Letters 35, 1661 (1999) and J. Chou et al. “Time-wavelength spectroscopy for chemical sensing,” IEEE Photonics Technology Letters 16, 1140 (2004)]
There may be a need to overcome at least some of the deficiencies and/or issues associated with the conventional arrangements and methods described above.